Cytotoxic pyrido[2,3,4-ki]acridine derivatives, their preparation and their therapeutic use

ABSTRACT

The invention provides compounds of formula (I)                    
     wherein 
     R 1  represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms, a halogen atom, a nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 6 carbon atoms, a dialkylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 6 carbon atoms, a dialkoxyamino group wherein each alkoxy moiety may be the same or different and each has from 1 to 6 carbon atoms, an alkanoyalmino group having from 1 to 20 carbon atoms or an alkanesulfonylamino group having from 1 to 6 carbon atoms; 
     R 2  represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms; and 
     R 3  represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms or an alkoxy group having from 1 to 6 carbon atoms; 
     and pharmaceutically acceptable salts thereof. The compounds exhibit activity against a wide variety of mammalian cancer cell lines.

This application is a 371 of PCT/GB00/02888 filed Jul. 27, 2000, now WO01/09133.

FIELD OF THE INVENTION

This invention relates to novel pyrido[2,3,4-k,l]acridine compounds. Theinvention also relates to their use in the treatment of cancers andprocesses for preparing them.

DESCRIPTION OF PRIOR ART

The polycyclic aromatic alkaloids based on the pyrido[2,3,4-k,l]acridineskeleton are a growing class of ascidian metabolites that often exhibita variety of interesting biological properties, including antitumouractivity, as reviewed by Molinksy (1993), Álvarez and Joule (1992),Álvarez et al (1991) and Groundwater and Munawar (1998). As examples ofthese alkaloids, there are described: norsegoline (Rudi et al, 1988),varamines (Molinsky and Ireland, 1989), Iissoclins (Searle and Molinsky,1994), diplamine (McDonald et al, 1994; Chryulu and McKee, 1989),isobutyramide (Molinksy, 1993), cystodytins (Kobayashi wt al, 1988 and1991), and pantherinine (Kim et al, 1993). The structures of thesecompounds are shown below.

Biological studies on pyridoacridines are severely limited due to theirvery low availability from natural sources, and therefore the study oftheir mechanism of action and the establishment of reliablestructure-activity relationships requires the development of efficientsynthetic routes.

SUMMARY OF INVENTION

The present inventors have developed an efficient process for producingcompounds containing the pyrido[2,3,4-k,l]acridine skeleton in a smallnumber of steps from commonly available starting materials. Furthermore,the novel compounds produced by the process exhibit activity against awide variety of mammalian cancer cell lines.

Therefore, in a first aspect, the invention provides compounds offormula (I):

wherein:

R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms,a halogen atom, a nitro group, an amino group, a monoalkylamino groupwherein the alkyl moiety has from 1 to 6 carbon atoms, a dialkylaminogroup wherein each alkyl moiety may be the same or different and eachhas from 1 to 6 carbon atoms, a monoalkoxyamino group wherein the alkoxymoiety has from 1 to 6 carbon atoms, a dialkoxyamino group wherein eachalkoxy moiety may be the same or different and each has from 1 to 6carbon atoms, an alkanoylamino group having from 1 to 20 carbon atoms oran alkanesulfonylamino group having from 1 to 6 carbon atoms;

R² represents a hydrogen atom or an alkyl group having from 1 to 6carbon atoms; and

R³ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms or an alkoxy group having from 1 to 6 carbon atoms;

and pharmaceutically acceptable salts thereof.

In a second aspect, this invention provides a pharmaceutical compositioncontaining as an active ingredient a compound of formula (I) as definedabove or a pharmaceutically acceptable salt thereof together with apharmaceutically acceptable carrier or diluent.

In a third aspect, the invention provides a method for treating a mammalaffected by a malignant tumour sensitive to a compound of formula (I) asdefined above, which comprises administering to a mammal in need of suchtreatment a therapeutically effective amount of a compound of formula(I), a pharmaceutically acceptable salt thereof or a pharmaceuticalcomposition thereof as defined above.

In a fourth aspect, the invention provides the use of a compound offormula (I) as defined above, or a pharmaceutically acceptable saltthereof in the manufacture of a medicament for the treatment orprophylaxis of malignant tumours.

In a fifth aspect, the invention provides a method for preparing acompound of formula (I) as defined above or a pharmaceuticallyacceptable salt thereof, described in more detail hereinafter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The compounds of formula (I) above are defined in more detail below.

The alkyl group may be a straight-chain or branched alkyl group having 1to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl and hexyl. Of thesegroups, alkyl groups having from 1 to 4 carbon atoms are preferred,particularly the methyl and ethyl groups, and the methyl group isespecially preferred.

The alkoxy group comprises an oxygen atom substituted by astraight-chain or branched alkyl group having 1 to 6 carbon atoms suchas those described and exemplified above. As examples of such groups,there may be mentioned the methyoxy, ethoxy, propoxy, isopropoxy,butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxygroups. Alkoxy groups having from 1 to 4 carbon atoms are preferred, andthe methoxy and ethoxy groups are especially preferred.

The monoalkylamino group comprises an amino group which is substitutedby an alkyl group having 1 to 6 carbon atoms such as those described andexemplified above. As examples of such groups there may be mentioned themethylamino, ethylamino, propylamino, isopropylamino, butylamino,pentylamino and hexylamino groups. Monoalkylamino groups wherein thealkyl group has from 1 to 4 carbon atoms are preferred.

The dialkylamino group comprises an amino group which is substituted bytwo alkyl group having 1 to 6 carbon atoms such as those described andexemplified above. The alkyl groups may be the same or different, butare preferably the same. As examples of such groups there may bementioned the dimethylamino, diethylamino, N-methylethylamino,diisopropylamino, dibutylamino, dipentylamino and dihexylamino.Dialkylamino groups wherein each alkyl group has from 1 to 4 carbonatoms are preferred.

The monoalkoxyamino group comprises an amino group which is substitutedby an alkoxy group having 1 to 6 carbon atoms such as those describedand exemplified above. The dialkoxyamino group comprises an amino groupwhich is substituted by two alkoxy group having 1 to 6 carbon atoms suchas those described and exemplified above. The alkoxy groups may be thesame or different, but are preferably the same.

The alkanoylamino group comprises an amino group which is substituted byan alkanoyl group having from 1 to 20 carbon atoms, examples of whichinclude the formyl, acetyl, propanoyl, butanoyl, pentanoyl,2,2-dimethylpropanoyl (pivaolyl), hexanoyl, heptanoyl, octanoyl,nonanoyl, decanoyl, dodecanoyl (lauroyl), tetradecanoyl (myristoyl),hexadecanoyl (palmitoyl), octadecanoyl (stearoyl) and icoscanoyl(arachidoyl) groups. Of the alkanoylamino groups, those groups havingfrom 1 to 6 carbon atoms, particularly from 1 to 4 carbon atoms, arepreferred, and the formylamino and acetylamino groups are especiallypreferred.

The alkanesulfonylamino group comprises an amino group which issubstituted by an alkanesulfonyl group, of which the alkyl part is astraight-chain or branched alkyl group having 1 to 6 carbon atoms suchas those described and exemplified above. Examples of suitablealkanesulfonylamino groups include the methanesulfonylamino,ethanesulfonylamino, propanesulfonylamino, butanesulfonylamino,pentanesulfonylamino and hexanesulfonylamino groups. Of these groups,alkanesulfonylamino groups having from 1 to 4 atoms, especially themethanesulfonylamino and ethanesulfonylamino groups, are preferred.

The compounds of the present invention contain a basic nitrogen atom,and may therefore form salts by addition with an acid. There is noparticular restriction on the nature of such salts, provided that, whenthe salt is used for therapeutic purposes, it must be pharmaceuticallyacceptable, ie the salt must be about as active, more active, or notunduly less active than the free base compound, and about as toxic, lesstoxic or not unduly more toxic than the free base compound. However,when the salt is used for non-therapeutic purposes (eg as anintermediate in the production of further compounds) even thisrestriction does not apply. Examples of such salts include salts ofhydrohalic acids such as hydrofluoric acid, hydrochloric acid,hydrobromic acid and hydroiodic acid; inorganic acid salts such asnitrate, perchlorate, sulfate and phosphate; salts of alkanesulfonicacids such as methanesulfonic acid, trifluoromethanesulfonic acid andethanesulfonic acid; salts of arylsulfonic acid such as benzenesulfonicacid and p-toluenesulfonic acid; salts of amino acids such as glutamicacid and aspartic acid; and salts of carboxylic acids such as aceticacid, fumaric acid, tartaric acid, oxalic acid, maleic acid, malic acid,succinic acid, benzoic acid, mandelic acid, ascorbic acid, lactic acid,gluconic acid and citric acid.

In one embodiment, the invention provides compounds of formula (I)wherein:

R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms,a halogen atom, a nitro group, an amino group, a monoalkylamino groupwherein the alkyl moiety has from 1 to 6 carbon atoms, a dialkylaminogroup wherein each alkyl moiety may be the same or different and eachhas from 1 to 6 carbon atoms, a monoalkoxyamino group wherein the alkoxymoiety has from 1 to 6 carbon atoms or a dialkoxyamino group whereineach alkoxy moiety may be the same or different and each as from 1 to 6carbon atoms,

R² represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms or an alkoxy group having from 1 to 6 carbon atoms; and

R³ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms or an alkoxy group having from 1 to 6 carbon atoms.

Of the compounds of the present invention, preferred are the compoundsof formula (I) and pharmaceutically acceptable salts thereof wherein:

R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms,a nitro group, an amino group, a monoalkylamino group wherein the alkylmoiety has from 1 to 6 carbon atoms, a dialkylamino group wherein eachalkyl moiety may be the same or different and each has from 1 to 6carbon atoms, an alkanoylamino group having from 1 to 20 carbon atoms oran alkanesulfonylamino group having from 1 to 6 carbon atoms;

R² represents a hydrogen atom or an alkyl group having from 1 to 4carbon atoms; and

R³ represents a hydrogen atom or an alkyl group having from 1 to 4carbon atoms.

More preferred are the compounds of formula (I) and pharmaceuticallyacceptable salts thereof wherein:

R¹ represents a hydrogen atom, an alkyl group having from 1 to 4 carbonatoms, a nitro group, an amino group, a monoalkylamino group wherein thealkyl moiety has from 1 to 4 carbon atoms, a dialkylamino group whereineach alkyl moiety may be the same or different and each has from 1 to 4carbon atoms, an alkanoylamino group having from 1 to 6 carbon atoms oran alkanesulfonylamino group having from 1 to 4 carbon atoms;

R² represents a hydrogen atom or a methyl group; and

R³ represents a hydrogen atom or a methyl group.

Even more preferred are the compounds of formula (I) andpharmaceutically acceptable salts thereof wherein:

R¹ represents a hydrogen atom, a nitro group, an amino group or analkanoylamino group having from 1 to 4 carbon atoms;

R² represents a hydrogen atom or a methyl group; and

R³ represents a hydrogen atom.

The following compounds are most preferred:

3H-6-methoxypyrido[2,3,4-kl]acridine;

3H-6-hydroxypyrido[2,3,4kl]acridine;

3H-6-methoxy-4-nitropyrido[2,3,4-kl]acridine;

3H-4-acetylamino-6-methoxypyrido[2,3,4-kl]acridine;

and pharmaceutically acceptable salts thereof.

Examples of pharmaceutical compositions include any solid (tablets,pills, capsules, granules, etc.) or liquid (solutions, suspensions oremulsions) formulations which are suitable for oral, topical orparenteral administration, and they may contain the pure compound or incombination with any carrier or other pharmacologically activecompounds. These compositions may need to be sterile when administeredparenterally.

The correct dosage of a pharmaceutical composition comprising compoundswith formula (I), will vary according to the pharmaceutical formulation,the mode of application, and the particular situs, host and tumour beingtreated. Other factors like age, body weight, sex, diet, time ofadministration, rate of excretion, condition of the host, drugcombinations, reaction sensitivities and severity of the disease shallbe taken into account. Administration can be carried out continuously orperiodically within the maximum tolerated dose.

The compounds of formula (I) may be prepared by a number of methodsknown to those in the art. For example, they may be prepared by reactinga compound of formula (II):

wherein:

R^(1a) represents any of the groups represented by R¹, and any groupwherein OH and NH groups (if any) are protected;

R^(2a) represents an alkyl group having from 1 to 6 carbon atoms or ahydroxy-protecting group; and

R⁴ represents a hydrogen atom, an alkyl group having from 1 to 6 carbonatoms or an alkoxy group having from 1 to 6 carbon atoms;

with a compound of formula (III):

M^(n+) [N(CHO)₂]_(n)  (III)

wherein M represents a Group 1 metal ion, a Group 2 metal ion or atetraalkylammonium ion (in which each alkyl group may be the same ordifferent and each has from 1 to 20 carbon atoms), and n stands for aninteger equal to the positive valency of M;

to give a compound of formula (Ia):

in which R^(1a) and R^(2a) are as defined above;

and, if necessary, removing protecting groups;

and, if necessary, any of the following steps (i) to (v);

(i) converting the group R^(1a) to any of the other groups representedby R¹;

(ii) where R² represents an alkyl group, alkylating the product;

(iii) where R³ represents an alkyl group, alkylating the product;

(iv) where R³ represents an alkoxy group, alkoxylating the product;

(v) salifying the product a give a pharmaceutically acceptable salt ofthe compound of formula (I).

In the compound of formula (II), R^(1a) represents any of the groupsrepresented by R¹, and any such group wherein OH and NH groups (if any)are protected, and R^(2a) represents an alkyl group having from 1 to 6carbon atoms or a hydroxy-protecting group.

The hydroxy-protecting group may be any such group used in the field oforganic synthetic chemistry. Suitable protecting groups are described inGreene and Wuts (1991). As non-limiting examples of thehydroxy-protecting group, there may be mentioned the following:

alkanoyl groups having from 1 to 20 carbon atoms such as those definedand exemplified above;

alkanoyl groups having from 1 to 20 carbon atoms which are substitutedwith a carboxy groups such as succinoyl, glutaroyl and adipoyl groups;

haloalkanoyl groups having from 1 to 20 carbon atoms such aschloroacetyl, dichloroacetyl, trichloroacetyl and trifluoroacetylgroups;

alkanoyl groups having from 2 to 20 carbon atoms which are substitutedwith one or more alkoxy groups having from 1 to 6 carbon atoms such asmethoxyacetyl groups;

aromatic acyl groups wherein the aromatic moiety is a carbocyclicaromatic group having from 6 to 10 ring carbon atoms (which may befurther substituted with one or more substituents selected from halogenatoms, alkyl groups having from 1 to 6 carbon atoms, alkoxy groupshaving from 1 to 6 carbon atoms, carboxy groups, nitro groups andalkoxycarbonyl groups having from 2 to 7 carbon atoms) such as2-bromobenzoyl, 4-chlorobenzoyl, 2,4,6-trimethylbenzoyl, 4-toluoyl,4-anisoyl, 2-carboxybenzoyl, 3-carboxybenzoyl 4-carboxybenzoyl,4-nitrobenzoyl, 2-nitrobenzoyl, 2-(methoxycarbonyl)-benzoyl groups;

tetrahydropyranyl, tetrahydrothiopyranyl, tetrahydrofuranyl ortetrahydrothiofuranyl groups (which may be optionally substituted withone or more substituents selected from halogen atoms, alkyl groupshaving from 1 to 6 carbon atoms and alkoxy groups having from 1 to 6carbon atoms) such as tetrahydropyran-2-yl, 3-bromotetrahydropyran-2-yl,4-methoxytetrahydropyran-4-yl, tetrahydrothipyran-2-yl and4-methoxytetrahydrothiopyran-4-yl, tetrahydrofuran-2-yl andtetrahydrothiofuran-2-yl groups;

silyl groups, for example, trialkylsilyl groups wherein each alkylmoiety has from 1 to 6 carbon atoms such as trimethylsilyl,triethylsilyl, isopropyldimethylsilyl, t-butyldimethylsilyl,methyldiisopropylsilyl, methyldi-t-butylsilyl and triisopropylsilylgroups and silyl groups substituted with 3 substituents selected fromaryl groups (as defined above in relation to aromatic acyl groups) andalkyl groups having from 1 to 6 carbon atoms such asdiphenylmethylsilyl, diphenylbutylsilyl, diphenylisopropylsilyl andphenyldiisopropylsilyl groups;

alkoxymethyl groups wherein the alkoxy moiety has from 1 to 6 carbonatoms and may be further substituted with a substituent selected fromalkoxy groups having from 1 to 6 carbon atoms and halogen atoms, forexample, methoxymethyl, 1,1-dimethyl-1-methoxymethyl, ethoxymethyl,propoxymethyl, isopropoxymethyl, butoxymethyl, t-butoxymethyl,2-methoxyethoxymethyl and 2,2,2-trichloromethoxymethyl groups;

ethyl groups substituted with a substituent selected from alkoxy groupshaving from 1 to 6 carbon atoms and halogen atoms, such as1-ethoxyethyl, 1-(isopropoxy)ethyl and 2,2,2-trichloroethyl groups;

aralkyl groups wherein an alkyl group having from 1 to 6 carbon atoms issubstituted with from 1 to 3 aryl groups as defined above in relation toaromatic acyl groups (which may be further substituted with one or moresubstituents selected from halogen atoms, alkyl groups having from 1 to6 carbon atoms, alkoxy groups having from 1 to 6 carbon atoms, carboxygroups, nitro groups, cyano groups or alkoxycarbonyl groups having from2 to 7 carbon atoms) such as benzyl, α-naphthylmethyl, β-naphthylmethyl,diphenylmethyl, triphenylmethyl and α-naphthyldiphenylmethyl groups suchas 4-methylbenzyl, 2,4,6-trimethylbenzyl, 3,4,5-trimethylbenzyl,4-methoxybenzyl, 4-methoxyphenyldiphenylmethyl, 2-nitrobenzyl,4-nitrobenzyl, 4-chlorobenzyl, 4-bromobenzyl, 4-cyanobenzyl, and4-cyanobenzyldiphenylmethyl groups.

The NH-protecting group may be any such group used in the field oforganic synthetic chemistry. Suitable protecting groups are described inGreene and Wuts (1991). As non-limiting examples of the NH-protectinggroup, there may be mentioned the following:

alkanoyl groups, carboxy-substituted alkanoyl groups, haloalkanoylgroups and alkoxy-substituted alkanoyl groups such as those defined andexemplified above in relation to hydroxy-protecting groups;

aromatic acyl groups wherein the aromatic moiety is a carboxylicaromatic group having from 6 to 10 carbon atoms (which may be furthersubstituted with one or more substituents selected from halogen atoms,alkyl groups having from 1 to 6 carbon atoms, alkoxy groups having from1 to 6 carbon atoms, cyano groups, carboxy groups, nitro groups,alkoxycarbonyl groups having from 2 to 7 carbon atoms) such as thosedefined and exemplified above in relation to hydroxy-protecting groups;

silyl groups such as those defined and exemplified above in relation tohydroxy-protecting groups;

aralkyl groups wherein an alkyl group having from 1 to 6 carbon atoms issubstituted with from 1 to 3 aryl groups as defined above in relation toaromatic acyl groups (which may be further substituted with one or moresubstituents selected from halogen atoms, alkyl groups having from 1 to6 carbon atoms, alkoxy groups having from 1 to 6 carbon atoms, carboxygroups, nitro groups, cyano groups or alkoxycarbonyl groups having from2 to 7 carbon atoms) such as those defined and exemplified above inrelation to hydroxy-protecting groups;

substituted methylene groups, each of which is capable of forming aSchiff base (>C═NH) such as N,N-dimethylaminomethylene, benzylidene,4-methoxybenzylidene, 4-nitrobenzylidene, salicylidene,5-chlorosalicylidene, diphenylmethylene and(5-chloro-2-hydroxphenyl)phenylmethylene groups.

The compound of formula (III) is a diformylamide compound, such aslithium diformylamide or sodium diformylamide, of which sodiumdiformylamide is preferred. The amount of the compound of formula (III)used is generally 1 to 5 molar equivalents, preferably 1.5 to 3 moreequivalents, of the compound of formula (II).

The reaction is generally and preferably carried out in the presence ofa solvent. There is no particular restriction on the nature of thesolvent, provided that it has no adverse effect on the reaction and candissolve the starting material therein to some extent. As non-limitingexamples of the solvent, there may be mentioned aromatic hydrocarbonssuch as benzene, toluene and xylene; aliphatic hydrocarbons such aspentane, hexane and heptane and mixtures thereof; halogenatedhydrocarbons such as dichloromethane, chloroform, carbon tetrachloride,dichloroethane, chlorobenzene and dichlorobenzene; esters such as ethylformate, ethyl acetate, propyl acetate, butyl acetate and diethylcarbonate; ethers such as diethyl ether, diisopropyl ether,tetrahydrofuran, dioxane, dimethoxyethane and diethylene glycol dimethylether; nitriles such as acetonitrile and isobutyronitrile; amides suchas formamide, N,N-dimethylformamide, N,N-dimethylacetamide,N-methyl-2-pyrrolidone and hexamethylphosphoric triamide; and sulfoxidessuch as dimethylsulfoxide and sulfolane. Of these, amides, especiallyN,N-dimethylformamide, are preferred.

The reaction temperature ranges from room temperature to 200° C., and ispreferably 100° C. to 170° C. In particular, when the solvent isN,N-dimethylformamide, the reaction temperature is most preferablybetween 140° C. and 160° C.

Although the reaction time varies depending on the reaction temperature,starting materials, reagents and nature of the solvent, it usuallyranges from 5 minutes to 3 hours, and is preferably from 10 minutes to 1hour, more preferably 20 to 40 minutes.

The compound of formula (II) may be prepared by the method described inScheme 1 below.

In the above Scheme 1, R^(1a), R^(2a) and R⁴ are defined above; Z is agroup capable of converting a hydroxy group into a leaving group (asdefined below), and R⁵ is a protecting group for an acetylenic hydrogen(as defined below).

Scheme 1 comprises three steps, each of which are described in moredetail below.

In Step A, an acridone compound of formula (IV):

in which R^(1a), R^(2a) and R⁴ are as defined above, is reacted with acompound of formula (V):

Z-Z′  (V)

in which:

Z is a group capable of converting a hydroxy group into a leaving group;and

Z′ is a leaving group.

to give a compound of formula (VI):

in which R^(1a), R^(2a) and R⁴ are as defined above.

Compounds of formula (IV) are known in the art. For example, thecompound of formula (IV) wherein R^(2a) is a methyl group and R⁴ is amethoxy group is described in Ionescu and Mester (1969).

In the compounds of formula (V), Z is a group capable of converting ahydroxy group into a leaving group. Any group known in the art to becapable of converting a hydroxy group into a leaving group may besuitable. As non-limiting examples of the group Z, there may bementioned alkanoyl groups having from 1 to 20 carbon atoms such as thosedefined and exemplified above in relation to alkanoylamino groups,alkanesulfonyl groups having from 1 to 6 carbon atoms such as thosedefined and exemplified above in relation to alkanesulfonylamino groups,arylsulfonyl groups such as the benzenesulfonyl group and thep-toluenesulfonyl group, and haloalkanesulfonyl groups wherein analkanesulfonyl group having from 1 to 6 carbon atoms such as thosedefined and exemplified above in relation to alkanesulfonylamino groupsis substituted in one or more (preferably all) substitutable positionsby a halogen atom, such as the trifluoromethanesulfonyl group and theperfluorobutanesulfonyl group. Of these, the trifluoromethanesulfonylgroup is especially preferred.

The group Z′ is a leaving group, and any leaving group known in the artmay be suitable. As non-limiting examples of the group Z′, there may bementioned halogen atoms such as chlorine, bromine and iodine, alkanoategroups wherein the alkanoyl part has from 1 to 20 carbon atoms such asthose defined and exemplified above in relation to alkanoylamino groups,alkanesulfonate groups having from 1 to 6 carbon atoms wherein thealkanesulfonyl part is defined and exemplified above in relation toalkanesulfonylamino groups, arylsulfonate groups such as thebenzenesulfonate and the p-toluenesulfonate group, orhaloalkanesulfonate groups wherein the haloalkanesulfonyl moiety isdefined and exemplified above, such as the trifluoromethanesulfonate ionand the perfluorobutane-sulfonate ion, of which thetrifluoromethanesulfonate ion is preferred.

The reaction is generally and preferably carried out in the presence ofa solvent. There is no particular restriction on the nature of thesolvent, provided that is has no adverse effect on the reaction and candissolve the starting material therein to some extent. As non-limitingexamples of the solvent, there may be mentioned aromatic hydrocarbonssuch as benzene, toluene and xylene; aliphatic hydrocarbons such aspentane, hexane and heptane and mixtures thereof; halogenatedhydrocarbons such as dichloromethane, chloroform, carbon tetrachloride,dichloromethane, chlorobenzene and dichloromethane; esters such as ethylformate, ethyl acetate, propyl acetate, butyl acetate and diethylcarbonate; ethers such as diethyl ether, diisopropyl ether,tetrahydrofuran, dioxane, dimethoxyethane and diethylene glycol dimethylether; nitriles such as acetonitrile and isobutyronitrile; amides suchas formamide, N,N-dimethylformamide, N,N-dimethylacetamide,N-methyl-2-pyrrolidone and hexamethylphosphoric triamide; and sulfoxidessuch as dimethylsulfoxide and sulfolane. Of these, halogenatedhydrocarbons, especially dichloromethane, are preferred.

The amount of the compound of formula (V) used is generally 1 to 5 molarequivalents, preferably 1.1 to 2 molar equivalents, of the compound offormula (IV).

The reaction is generally carried out in the presence of a base, andsimilarly there is no particular restriction on the nature of the base,provided it is capable of acting as a base (in particular, to neutraliseany acidic by-product formed in the reaction). However, weak bases, iethose for which pK_(a) of the conjugate acid is greater than 0 (thosewhich would not fully ionise in solution) are preferred. As non-limitingexamples of the base there may be mentioned alkali metal carbonates andhydrogencarbonates such as sodium carbonate, potassium carbonate andsodium hydrogencarbonate, aliphatic and heterocyclic amines such astrimethylamine, triethylamine, N,N-diisopropylethylamine, tributylamine,pyrrolidine, piperidine and 1,8-diazabicyclo[5.4.0]-7-undecene, andaromatic and heteroaromatic amines such as pyridine,2,6-dimethylpyridine (2,6-lutidine) and 4-(N,N-dimethylamino)pyridine(DMAP), of which the heteroaromatic amines are preferred. The amount ofbase used is generally 1 to 5 molar equivalents, preferably 1.1 to 3molar equivalents, of the compound of formula (IV).

The reaction may be carried out in the presence of a catalyst,particularly a nucleophilic catalyst. Although any suitable catalyst maybe used, 4-(N,N-dimethylamino)pyridine (DMAP) is preferred. The amountof catalyst used is generally 0.05 to 0.5 molar equivalents, preferably0.1 to 0.3 molar equivalents, of the compound of formula (IV).

The reaction temperature ranges from −20° C. to 100° C., preferably 0°C. to 50° C.

Although the reaction time varies depending on the reaction temperature,starting material compounds, reagents and nature of the solvent, itusually ranges from 10 minutes to 3 days, preferably from 30 minutes to12 hours.

In Step B, the compound of formula (VI) defined above is reacted with acompound of formula (VII):

H—C≡C—R⁵  (VII)

in which R⁵ is a protecting group for an acetylenic hydrogen, to give acompound of formula (VIII):

in which R¹, R^(2a), R⁴ and R⁵ are as defined above.

In the compounds of formula (VII), the group R⁵ is a protecting groupfor an acetylenic hydrogen. Any group known in the art to be suitablefor protecting an acetylenic hydrogen may be used. However, silyl groupssuch as those defined and exemplified above in relation tohydroxy-protecting groups are preferred and the trimethysilyl group isespecially preferred.

The amount of the compound of formula (VII) used is generally 1 to 10molar equivalents, preferably 2 to 5 molar equivalents, of the compoundof formula (VI).

The reaction is generally and preferably carried out in the presence ofa solvent. There is no particular restriction on the nature of thesolvent, provided that is has no adverse effect on the reaction and candissolve the starting material therein to some extent. As non-limitingexamples of the solvent, there may be mentioned aromatic hydrocarbonssuch as benzene, toluene and xylene; aliphatic hydrocarbons such aspentane, hexane and heptane and mixtures thereof; halogenatedhydrocarbons such as dichloromethane, chloroform, carbon tetrachloride,dichloromethane, chlorobenzene and dichloromethane; esters such as ethylformate, ethyl acetate, propyl acetate, butyl acetate and diethylcarbonate; ethers such as diethyl ether, diisopropyl ether,tetrahydrofuran, dioxane, dimethoxyethane and diethylene glycol dimethylether; nitriles such as acetonitrile and isobutyronitrile; amides suchas formamide, N,N-dimethylformamide, N,N-dimethylacetamide,N-methyl-2-pyrrolidone and hexamethylphosphoric triamide; and sulfoxidessuch as dimethylsulfoxide and sulfolane. Of these, ethers, especiallytetrahydrofuran, are preferred.

The reaction is generally carried out in the presence of a base, andsimilarly there is no particular restriction on the nature of the base,provided it is capable of acting as a base (in particular, to neutraliseany acidic by-product formed in the reaction). However, weak bases (asdefined above) are preferred. As non-limiting examples of the base theremay be mentioned alkali metal carbonates and hydrogencarbonates such assodium carbonate, potassium carbonate and sodium hydrogencarbonate,aliphatic and heterocyclic amines such as trimethylamine, triethylamine,N,N-diisopropylamine, tributylamine, pyrrolidine, piperidine and1,8-diazabicyclo[5.4.0]-7-undecene, and aromatic and heteroaromaticamines such as pyridine, 2,6-dimethylpyridine (2,6-lutidine) and4-(N,N-dimethylamino)pyridine (DMAP), of which aliphatic amines,especially N,N-diisopropylethylamine, are preferred. The amount of baseused is generally 1 to 10 molar equivalents, preferably 2 to 6 molarequivalents, of the compound of formula (VI).

The reaction is preferably carried out in the presence of a catalyst,and any substance capable of catalysing the reaction may be used.However, palladium compounds, especiallytetrakis(triphenylphosphine)palladium (0), are preferred. The amount ofcatalyst used is generally 0.001 to 0.5 molar equivalents, preferably0.01 to 0.2 molar equivalents, of the compound of formula (VI).

The reaction temperature ranges from room temperature to 100° C., and ispreferably 50° C. to 80° C. In particular, when the solvent istetrahydrofuran, the reaction temperature is between 65° C. and 70° C.

Although the reaction time varies depending on the reaction temperature,starting material compounds, reagents and nature of the solvent, itusually ranges from 10 minutes to 3 days, and is preferably from 30minutes to 12 hours, more preferably 2 hours to 8 hours.

In Step C, the protecting group R⁵ of the compound of formula (VIII) isremoved to produce a compound of formula (II).

The nature of the reagent used depends on the nature of the protectinggroup R⁵ to be removed. However, when the protecting group R⁵ is a silylgroup, the group may be removed under acidic conditions (for example,but not limited to acetic acid, or hydrochloric acid or citric acid),basic conditions (for example, but not limited to potassium carbonate),or using a source of fluoride ion (for example, but not limited totetrabutylammonium fluoride, sodium fluoride, potassium fluoride,hydrofluoric acid, HF-pyridine, HF-triethylamine). Removal of theprotecting group using a source of fluoride ion is preferred and the useof potassium fluoride or tetrabutylammonium fluoride is especiallypreferred.

The amount of the reagent used to remove the protecting group R⁵ dependson the nature of the protecting group R⁵ to be removed. However, whenthe protecting group R⁵ is a silyl group, the amount of the reagent usedis generally 1 to 10 molar equivalents, preferably 2 to 5 molarequivalents, of the compound of formula (VII).

The reaction is generally and preferably carried out in the presence ofa solvent. There is no particular restriction on the nature of thesolvent, provided that it has no adverse effect on the reaction and candissolve the starting material therein to some extent. As non-limitingexamples of the solvent, there may be mentioned water, alcohols such asmethanol, ethanol, isopropanol and t-butanol, aromatic hydrocarbons suchas benzene, toluene and xylene; aliphatic hydrocarbons such as pentane,hexane and heptane and mixtures thereof; halogenated hydrocarbons suchas dichloromethane, chloroform, carbon tetrachloride, dichloroethane,chlorobenzene and dichlorobenzene; esters such as ethyl formate, ethylacetate, propyl acetate, butyl acetate and diethyl carbonate; etherssuch as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane,dimethoxyethane and diethylene glycol dimethyl ether; nitriles such asacetonitrile and isobutyronitrile; amides such as formamide,N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone andhexamethylphosphoric triamide; and sulfoxides such as dimethylsulfoxideand sulfolane. Of these, alcohols, especially methanol, and ethers,especially tetrahydrofuran, are preferred.

The compound of formula (II) may then be reacted with a compound offormula (III) to produce a compound of formula (I) as described above.Further compounds of formula (I) may be prepared be derivatising anothercompound of formula (I).

Preparation of the compounds of the invention are described in theExamples below.

Preparation of the starting materials is described in the Preparations.

EXAMPLES

General Experimental Details

Melting points were determined in a capillary tube and are uncorrected.TLC was carried out on SiO₂ (silica gel 60 F₂₅₄, Merck 0.063-0.200 mm)and spots were located with UV light. Column chromatography was carriedout on SiO₂ (silica gel 60 SDS 0.060-0.2 mm). Flash chromatography wascarried out on SiO₂ (silica gel 60 A CC, Merck). Organic extracts weredried with anhydrous Na₂SO₄, and solutions were evaporated under reducedpressure with a rotary evaporator. Infra-red (IR) spectra were performedwith a Nicolet 205 FT-IR; data are given in wavenumbers (v) in cm⁻¹using the following abbreviations: s: strong; m, medium; w, weak.Nuclear magnetic resonance (NMR) spectra were measured with VarianGemini-200 (200 MHz), Varian Gemini-300 (300 MHz) and Varian VXR-500(500 MHz) spectrometers; chemical shift data (δ) are given in parts permillion (ppm) referenced to tetramethylsilane and using the followingabbreviations: s, singlet; d, doublet; t, triplet; q, quartet. For thecompounds of Examples 1 to 4, the carbons are numbered as outlined inthe skeleton structure below. Mass spectra were measured in the electronimpact (EI) or chemical ionization (CI) mode with a Hewlett-Packardmodel 5989A. High resolution mass spectra were performed with anAutospec/VG by the Department de Química Orgànica Biològica (CSIC)Barcelona. Elemental analyses were performed with a C E InstrumentsEA-1108 in the Serveis Científico-Tècnics de la Universitad deBarcelona.

Example 1 3H-6-Methoxypyrido[2,3,4-kl]acridine

Sodium diformylamide (190 mg, 2.0 mmol) was added to a solution of1,4-dimethoxy-9-ethynylacridine (prepared as described in Preparation 3below) (217 mg, 0.8 mmol) in dry DMF (2 ml) and the mixture was stirredat reflux for 30 min. The solvent was removed and the residue wasdissolved in CH₂Cl₂ and washed with H₂O. The organic solution was driedand evaporated affording a residue which was purified by columnchromatography. Elution with CH₂Cl₂/MeOH (99:2) gave the title compound(109.5 mg, 55%); m.p. 148-150° C. (EtOAc). IR (KBr): v/cm⁻¹=1686 (s,C═N), 1599 (s, Ar), 1573 (s, Ar), 1460 (s, Ar); ¹H NMR (500 MHz, CDCl₃):δ_(H)/ppm=3.85 (s, 3H, OCH₃), 6.75 (d, J=7.8 Hz, 1H, H-8), 6.85 (dd,J=8.0 and 7.5 Hz, 1H-10), 6.99 (d, J=5.0 Hz, 1H, H-1), 7.18 (dd, J=7.8and 7.5 Hz, 1H, H-9), 7.20 (d, J=9.0 Hz, 1H, H-4), 7.23 (d, J=9.0 Hz,1H, H-5), 7.66 (d, J=8.0 Hz, 1H, H-11), 8.37 (d, J=5.0 Hz, 1H, H-2); ¹³CNMR (50.3 MHz, CDCl₃): δ_(C)/ppm=56.3 (q, OCH₃), 106.1 (d, C-1), 115.1(d, C-4), 115.3 (d, C-5), 115.6 (d, C-8), 117.4 (s, C-11a), 118.7 (s,C-11c), 121.0 (d, C-10), 123.9 (d, C-11), 125.2 (s, C-6), 131.5 (d,C-9), 137.2 (s, C-6a), 139.2 (2s, C-7a and C-11b), 144.5 (s, C-3a),150.3 (d, C-2); MS (EI); m/z (%)=249 [M+1] (11), 248 [M⁺] (45), 234(21), 233 (100); HRMS: calcd, for C₁₆H₁₂N₂O 248.0949; found 248.0938;Elemental analysis: C₁₆H₁₂N₂O.0.5CH₃CO₂C₂H₅ (292.35): calcd. C 73.95, H5.52, N 9.58; found C 73.67, H 5.42, N, 9.64.

Example 2 3H-6-Hydroxypyrido[2,3,4-kl]acridine

Boron tribromide (8.3 ml, 8.3 mmol) was added to a solution of3H-6-methoxypyrido[2,3,4-kl]acridine (prepared as described in Example 1above) (0.4 g, 1.6 mmol) in CH₂Cl₂ (20 mil) cooled at −78° C. andmaintained under nitrogen. The reaction temperature was increasedgradually to −30° C. during 90 min and then to room temperature during30 min. The reaction mixture was neutralised with saturated aq. Na₂CO₃and extracted with CH₂Cl₂. The organic solution was dried and evaporatedto give the title compound as a gum. IR (KBr): v/cm⁻¹=3440 (s, OH andNH), 1588 (s, Ar), 1318 (s, Ar), 1052 (s, Ar); ¹H NMR (300 MHz, CD₃OD):δ_(H)/ppm=6.92 (d, J=8.7 Hz, 1H, H-4), 7.04 (d, J=6.5 Hz, 1H, H-1), 7.09(dd, J=8.5 and 7.1 Hz, 1H, H-10), 7.28 (d, J=8.4 Hz, 1H, H-8), 7.33 (d,J=8.7 Hz, 1H, H-5), 7.51 (dd, J=8.4 and 7.1 Hz, 1H, H-9), 7.79 (d, J=8.5Hz, 1H, H-11), 7.93 (d, J=6.5 Hz, 1H, H-2); ¹³C NMR (75.4 MHz, CD₃OD):δ_(C)/ppm=104.1 (d, C-1), 106.1 (d, C-4), 116.3 (s, C-11a), 118.6 (d,C-5), 121.1 (s, C-6b), 121.6 (d, C-8), 124.0 (d, C-10), 126.1 (d, C-11),127.0 (s, C-11b), 132.9 (s, C-7a), 136.1 (d, C-9), 139.5 (s, C-6a),141.8 (s, C-3a), 143.2 (d, C-2), 150.3 (s, C-6); MS (EI); m/z (%)=235[M+1] (26) [M⁺] (100), 205 (27), 117 (17); HRMS: calcd. for C₁₅H₁₀N₂O234.0793; found 234.0790.

Example 3 6-Methoxy-4-nitro-3H-pyrido[2,3,4-kl]acridine

A solution of Cu(NO₃)₂ (144 mg, 0.6 mmol) in Ac₂O (6 ml) was added to asolution of 3H-6-methoxypyrido[2,3,4-kl]acridine (prepared as describedin Example 1 above) (100 mg, 0.4 mmol) in Ac₂O (3 ml) cooled at 0° C.and the mixture was stirred for 3 h at the same temperature. AqueousNaOH (50%) was added until basic and the mixture was extracted withCH₂Cl₂. The organic solution was dried and evaporated to give a crudeproduct which was purified by column chromatography. Elution withCH₂Cl₂:MeOH (99:1) affords the title compound (60 mg, 51%), m.p.220-223° C. (CH₂Cl₂). IR (KBr): ν/cm⁻¹=3390, 1609, 1578, 1263; ¹H-NMR(500 MHz, CDCl₃): δ_(H)/ppm=4.12 (s, 3H, OCH₃), 5.40 (s, 1H, H-5), 7.83(ddd, J=7.7, 7.5 and 0.5 Hz, 1H, H-10), 7.92 (ddd, J=7.7, 7.5 and 0.5Hz, 1H, H-9), 8.40 (dd, J=7.7 and 0.5 Hz, 1H, H-8), 8.51 (d, J=5.5 Hz,1H, H-1), 8.56 (dd, J=7.7 and 0.5 Hz, 1H, H-11), 9.19 (d, J=5.5 Hz, 1H,H-2), ¹³C-NMR (75.4 MHz, CDCl₃): 67 _(C)/ppm=57.0 (q, OCH₃), 108.1 (d,C-5), 118.5 (s, C-11c), 118.8 (d, C-1), 122.3 (s, C-11a), 122.9 (d,C-11), 130.0 (d, C-10), 131.7 (d, C-9), 132.0 (d, C-8), 137.1 (s,C-11b), 145.1 (s, C-7a), 146.6 (s, C-3a), 149.8 (d, C-2), 164.4 (s,C-6), 183.3 (s, C-6a), MS (EI): m/z (%)=293 [M⁺] (4), 262 (42), 233(52), 205 (100); HRMS calculated for C₁₆H₁₁N₃O₃ 293.0800; found293.0798.

Example 4 4-Acetylamino-6-methoxy-3H-pyrido[2,3,4-kl]acridine

A solution of 6-methoxy-4-nitro-3H-pyrido[2,3,4-kl]acridine (prepared asdescribed in Example 3 above) (136 mg, 0.5 mmol) and SnCl₂ (0.5 g, 2.0mmol) in MeOH (5 ml) was refluxed for 2 h. The solvent was evaporatedunder vacuum, the residue was dissolved in Ac₂O (10 ml) and theresulting solution was refluxed for 30 min. The excess of Ac₂O wasevaporated under vacuum, the residue was dissolved in CH₂Cl₂ and theorganic solution was washed with saturated NaHCO₃. The organic layer wasdried and evaporated giving the title compound (78 mg, 55%), m.p.128-132° C. (CH₂Cl₂). IR (KBr): ν/cm⁻¹=2939, 1600, 1461, 1365, 1205;¹H-NMR (200 MHz, CDCl₃): δ_(H)/ppm=3.95 (s, 3H, OCH₃), 6.91 (dd, J=8.6and 1.0 Hz, 1H, H-8), 7.00 (ddd, J=8.2, 7.6 and 1.0 Hz, 1H, H-10), 7.09(d, J=5.1 Hz, 1H, H-1), 7.18 (s, 1H, H-5), 7.34 (ddd, J=8.6, 7.6 and 1.4Hz, 1H, H-9); 7.76 (dd, J=8.2 and 1.4 Hz, 1H, H-11); 8.48 (d, J=5.1 Hz,1H, H-2); ¹³C-NMR (CDCl₃, 75.4 MHz); δ_(C)/ppm=56.4 (q, OCH₃), 106.5 (d,C-5), 109.1 (d, C-1), 115.8 (d, C-8), 121.2 (d, C-10), 123.8 (d, C-11),131.7 (d, C-9), 150.4 (d, C-2), 170.2 (s, C═O); MS (EI): m/z (%)=306[M+1] (15); 305 [M⁺] (1); 249 (100); HRMS calculated for C₁₈H₁₆N₃O₂306.1242; found 306.1255.

Preparation 1 1,4-Dimethoxy-9-trifluoromethylsulfonyloxyacridine

To a solution of 1,4-dimethoxyacridine (prepared as described in Ionescuand Mester (1969)) (1.0 g, 3.9 mmol) in dry CH₂Cl₂ (18 ml) under N₂ weresuccessively added DMAP (95 mg, 0.8 mmol), 2,6-lutidine (0.6 ml, 55mmol) and trifluoromethane-sulfonic anhydride (0.8 ml, 4.7 mmol) and thereaction mixture was stirred at 0° C. for 2 h and then for 1 h at rt.The solution was washed with H₂O, dried and evaporated. The residue waspurified by column chromatography when elution with hexane/CH₂Cl₂ (1:1)to give the title compound (1.3 g, 87%), as a yellow solid. IR (KBr):ν/cm⁻¹=1253 (s, SO), 1030 (s, SO); ¹H NMR (200 MHz, CDCl₃):δ_(H)/ppm=4.04 (s, 3H, OCH₃), 4.14 (s, 3H, OCH₃), 6.83 (d, J=8.4 Hz, 1H,H-2), 7.01 (d, J=8.4 Hz, 1H, H-3), 7.68 (dd, J=8.5 and 7.8 Hz, 1H, H-7),7.86 (dd, J=8.5 and 7.8 Hz, 1H, H-6), 8.22 (d, J=8.5 Hz, 1H, H-5), 8.43(d, J=8.5 Hz, 1H, H-8); ¹³C NMR (50.3 MHz, CDCl₃): δ_(C)/ppm=55.2 (q,OCH₃) 56.3 (q, OCH₃), 104.2 (d, C-2), 106.6 (d, C-3), 113.3 (s, C-9a),118.5 (q, CF₃), 119.1 (s, C-8a), 120.7 (d, C-7), 122.5 (s, C-4a), 127.6(d, C-6), 129.8 (d, C-8), 130.9 (d, C-5), 144.2 (s, C-10a), 147.2 (s,C-1), 148.7 (s, C-4), 148.8 (s, C-9); MS (EI); m/z (%)=388 [M+1] (9),387 [M+] (42), 254 (100), 226 (69); HRMS: calcd. for C₁₆H₁₂F₃NO₅S387.0388; found 387.0394.

Preparation 2 1,4-Dimethoxy-9-trimethylsilylethynylacridine

To a solution of 1,4-dimethoxy-9-trifluoromethylsulfonyloxyacridine(prepared as described in Preparation 1 above) (1.2 g, 3.1 mmol) in drytetrahydrofuran (10 ml) under N₂ were successively addedtetrakis(triphenylphosphine) palladium (0), (0.3 g, 0.3 mmol),N,N-diisopropylethylamine (1.6 ml, 9.3 mmol) and trimethylsilylacetylene(1.3 ml, 9.3 mmol). The mixture was stirred at reflux for 5 h. Afterthis time the solvent was evaporated and the residue was dissolved inCH₂Cl₂ and washed with water. The organic solution was dried anevaporated affording a residue which was purified by columnchromatography. Elution with hexane/CH₂Cl₂ (1:1) gave the title compound(1.0 g, 98%) as a red solid; m.p. 110-111° C. (CH₂Cl₂). IR (film):ν/cm⁻¹=2810 (w, C≡C), 1608 (s, Ar), 1527 (m, Ar), 1468 (s, Ar); ¹H NMR(200 MHz, CDCl₃): δ_(H)/ppm=0.41 (s, 9H, 3×CH₃), 3.99 (s, 3H, OCH₃),4.11 (s, 3H, OCH₃), 6.75 (d, J=8.4 Hz, 1H, H-2), 6.93 (d, J=8.4 Hz, 1H,H-3), 7.63 (dd, J=8.0 and 7.2 Hz, 1H, H-7), 7.78 (dd, J=8.4 and 7.2 Hz,1H, H-6), 8.35 (d, J=8.4 Hz, 1H, H-5), 8.64 (d, J=8.0 Hz, 1H, H-8); ¹³CNMR (50.3 MHz, CDCl₃): δ_(C)=0.0 (q, CH₃), 55.8 (q, OCH₃), 56.1 (q,OCH₃), 101.5 (s, ≡C—Si), 103.9 (d, C-2), 105.7 (d, C-3), 111.8 (s, ≡C),120.5 (s, C-9a), 126.4 (d, C-7), 126.9 (d, C-6), 127.5 (s, C-9), 129.9(d, C-5), 130.0 (s, C-8a), 130.3 (d, C-8), 142.1 (s, C-4a), 147.0 (s,C-1), 149.4 (s, C-4 and C-10a); MS (EI); m/z (%)=336 [M+1] (10), 335[M⁺] (36), 320 (100), 306 (13), 290 (10), 262 (14); HRMS: calcd. forC₂₀H₂₁NO₂Si 335.1341; found 335.1336; Elemental analysis:C₂₀H₂₁NO₂Si.0.125CH₂Cl₂ (346.10): calcd. C 69.84, H, 6.19, N, 4.05;found C 69.70, H 6.42, N 4.09.

Preparation 3 1,4-Dimethoxy-9-ethynylacridine

Potassium fluoride (0.5 g, 9.0 mmol) was added to a solution of1,4-dimethoxy-9-trimethylsilylethynylacridine (prepared as described inPreparation 2 above) (1 g, 3.0 mmol) in methanol (30 ml) and the mixturewas stirred at reflux for 30 min. The solvent was evaporated and theresidue was dissolved in CH₂Cl₂. The organic solution was washed withH₂O, dried and evaporated to give the title compound (764 mg, 97%) as abrown solid; m.p. 155-157° C. (Et₂O). IR (KBr): ν/cm⁻¹=2100 (w, C≡C),1625 (m, Ar), 1460 (m, Ar); ¹H NMR (200 MHz, CDCl₃): δ_(H)/ppm=3.98 (s,3H, OCH₃), 4.10 (s, 3H, OCH₃), 4.20 (s, 1H, ≡CH), 6.75 (d, J=8.4 Hz, 1H,H-2), 6.92 (d, J=8.4 Hz, 1H, H-3), 7.62 (dd, J=8.4 and 7.4 Hz, 1H, H-7),7.78 (dd, J=8.6 and 7.4 Hz, 1H, H-6), 8.36 (d, J=8.6 Hz, 1H, H-5), 8.66(d, J=8.4 Hz, 1H, H-8); ¹³C NMR (75.4 MHz, CDCl₃): δ_(C)/ppm=56.0 (q,OCH₃), 56.1 (q, OCH₃), 85.6 (s, ≡C), 92.7 (d, ≡C), 104.1 (d, C-2), 105.8(d, C-3), 121.0 (s, C-9a), 124.2 (s, C-9), 126.2 (d, C-6), 127.1 (d,C-7), 127.8 (s, C-8a), 130.0 (d, C-8), 130.4 (d, C-5), 141.3 (s, C-4a),147.5 (s, C-1), 149.3 (s, C-10a), 149.5 (s, C-4); MS (EI); m/z (%)=264[M+1] (7), 263 [M⁺] (35), 248 (100); HRMS: calcd. for C₁₇H₁₃NO₂263.0946; found 263.0940.

BIOLOGICAL ACTIVITY

The compounds of the present invention exhibit antitumour activityagainst cell lines derived from human solid tumours, such as human lungcarcinoma, human colon carcinoma and human melanoma, and, the like, theyare active against other tumour cell lines, like leukemia and lymphoma.

The antitumour activity of the compounds of the present invention hasbeen detected in vitro by culturing the tumour cells following themethodology described in Bergeron et al (1984), and by Schroeder et al(1981). Activity against different tumours as mouse lymphoma, human NSClung carcinoma, human melanoma and human colon carcinoma has beenobserved.

Some tumours were more sensitive than others. As for example it wasfound that NSC lung carcinoma and melanoma cells were 100 times moresensitive than mouse lymphoma and 1000 times more sensitive than humancolon carcinoma cells.

Example

Biological activity: cells were maintained in logarithmic phase ofgrowth in Eagle's Minimum Essential Medium, with Earle's Balanced Salts,with 2.0 mM L-glutamine, with non-essential amino acids, without sodiumbicarbonate (EMEM/neaa); supplemented with 10% Fetal Calf Serium (FCS),10⁻² M sodium bicarbonate and 0.1 g/l penicillin-G+streptomycin sulfate.

The tumour cell lines employed have been P-388D₁ (ATCC CCL-46,suspension culture of a lymphoid neoplasm from DBA/2 mouse), A549 (ATCCCCL-185, monolayer culture of a human lung carcinoma), HT-29 (ATCCHTB-38, monolayer culture of a human colon carcinoma) and SK-MEL-28(ATCC HTB-72, monolayer culture of a human melanoma).

P-388D₁ cells were seeded into 16 mm wells at 1×10⁴ cells per well in 1ml aliquots of MEM 5FCS containing the indicated concentration of drug.A separate set of cultures without drug was seeded as control growth toensure that cells remained in expotential phase of growth. Alldeterminations were carried out in duplicate. After three days ofincubation at 37° C., 10% CO₂ in a 98% humid atmosphere, an approximateIC₅₀ was determined by comparing the growth in wells with drug to thegrowth in wells control.

A549, HT-29 and SK-MEL-28 were seeded into 16 mm wells at 2×10⁴ cellsper well in 1 ml aliquots of MEM 10FCS containing the indicatedconcentration of drug. A separate set of cultures without drug and wasseeded as control growth to ensure that cells remained in exponentialphase of growth. All determinations were carried out in duplicate. Afterthree days of incubation at 37° C., 10% CO₂ in a 98% humid atmosphere,the wells were stained with 0.1% Crystal Violet. An approximate IC₅₀ wasdetermined by comparing the growth in wells with drug to the growth inwells control.

In Table 1 are presented the cytoxicity expressed as IC₅₀ (μM)

TABLE 1 IC₅₀ (μM) P-388D₁ A549 HT-29 SK-MEL-28 ATCC ATCC- ATCC ATCCCOMPOUND CCL-46 CCL-L-185 HTB-38 HTB-72 Example 1 0.50 0.05 0.50 0.05Example 3 0.34 0.03 0.34 0.03 Example 4 1.64 0.03 1.64 0.03

REFERENCES

The following articles have been cited herein, and they are incorporatedherein by reference:

T. F. Molinsky, Chem. Rev. 1993, 93, 1825.

M. Álvarez, J. A. Joule, Heterocycles, 1992, 34, 2385.

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A. Rudi, Y. Benayahu, Y. Kashman J. Org. Chem. 1989, 54, 5331.

T. F. Molinsky, C. M. Ireland J. Org. Chem. 1989, 54, 4256.

P. A. Searle, T. F. Molinsky J. Org. Chem. 1994, 59, 6600.

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T. F. Molinksy, Chem. Rev. 1993, 93, 1825.

J. Kobayashi, J. Cheng, M. R. Walchli, H. Nakamura, Y. Hirata, T.Sasaki, Y. Ohizumi J. Org. Chem. 1988, 53, 1800.

J. Kobayashi, M. Tsuda, A. Tanabe, M. Ishibashi, J. F. Cheng, Y.Yamamura, T. Sasaki, J. Nat. Prod. 1991, 54, 1634.

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T. W. Greene, P. G. M. Wuts, “Protecting Groups in Organic Synthesis”,John Wiley & Sons, 1991.

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What is claimed is:
 1. A compound of formula (I):

wherein: R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms, a halogen atom, a nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 6 carbon atoms, a dialklylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 6 carbon atoms, a monoalkoxyamino group wherein the alkoxy moiety has from 1 to 6 carbon atoms, a dialkoxyamino group wherein each alkoxy moiety may be the same or different and each has from 1 to 6 carbon atoms, an alkanoylamino group having from 1 to 20 carbon atoms or an alkanesulfonylamino group having from 1 to 6 carbon atoms; R² represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms; and R³ represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms or an alkoxy group having from 1 to 6 carbon atoms; and pharmaceutically acceptable salts thereof.
 2. A compound according to claim 1, in which R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms, a nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 6 carbon atoms, a dialkylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 6 carbon atoms, an alkanoylamino group having from 1 to 20 carbon atoms or an alkanesulfonylamino group having from 1 to 6 carbon atoms.
 3. A compound according to claim 1, in which R¹ represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, a nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 4 carbon atoms, a dialkylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 4 carbon atoms, an alkanoylamino group having from 1 to 6 carbon atoms or an alkanesulfonylamino group having from 1 to 4 carbon atoms.
 4. A compound according to claim 1, in which R¹ represents a hydrogen atom, a nitro group, an amino group or an alkanoylamino group having from 1 to 4 carbon atoms.
 5. A compound according to claim 1, in which R² represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms.
 6. A compound according to claim 1, in which R² represents a hydrogen atom or a methyl group.
 7. A compound according to claim 1, in which R³ represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms.
 8. A compound according to claim 1, in which R³ represents a hydrogen atom or a methyl group.
 9. A compound according to claim 1, in which R³ represents a hydrogen atom.
 10. A compound according to claim 1, in which: R¹ represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 6 carbon atoms, a nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 6 carbon atoms, a dialkylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 6 carbon atoms, an alkanoylamino group having from 1 to 20 carbon atoms or an alkanesulfonylamino group having from 1 to 6 carbon atoms; R² represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms; and R³ represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms.
 11. A compound according to claim 1, in which: R¹ represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an nitro group, an amino group, a monoalkylamino group wherein the alkyl moiety has from 1 to 4 carbon atoms, a dialkylamino group wherein each alkyl moiety may be the same or different and each has from 1 to 4 carbon atoms, an alkanoylamino group having from 1 to 6 carbon atoms or an alkanesulfonylamino group having from 1 to 4 carbon atoms; R² represents a hydrogen atom or a methyl group; and R³ represents a hydrogen atom or a methyl group.
 12. A compound according to claim 1, in which: R¹ represents a hydrogen atom, a nitro group, an amino group or an alkanoylamino group having from 1 to 4 carbon atoms; R² represents a hydrogen atom or a methyl group; and R³ represents a hydrogen atom.
 13. A compound according to claim 1, selected from the following: 3H-6-methoxypyrido[2,3,4-kl]acridine; 3H-6-hydroxypyrido[2,3,4-kl]acridine; 3H-6-methoxy-4-nitropyrido[2,3,4-kl]acridine; 3H-4-acetylamino-6-methoxypyrido[2,3,4-kl]acridine; and pharmaceutically acceptable salts thereof.
 14. A pharmaceutical composition containing as an active ingredient a compound of formula (I) as defined in any one of claims 1 to 13 or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable carrier or diluent.
 15. A method for treating a mammal affected by a malignant tumour, which comprises administering to a mammal in need of such treatment a therapeutically effective amount of a compound of formula (I), a pharmaceutically acceptable salt thereof as defined in any one of claims 1 to 13 or a pharmaceutical composition thereof as defined in claim
 14. 16. A method for preparing a compound of formula (I) as defined in any one of claims 1 to 13 or a pharmaceutically acceptable salt thereof, comprising the following steps: reacting a compound of formula (II):

wherein: R^(1a) represents any of the groups represented by R¹, and any group wherein OH and NH groups (if any) are protected; R^(2a) represents an alkyl group having from 1 to 6 carbon atoms or a hydroxy-protecting group; and R⁴ represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms or an alkoxy group having from 1 to 6 carbon atoms; with a compound of formula (III): M^(n+) [N(CHO)₂]_(n)  (III) wherein M represents a Group 1 metal ion, a Group 2 metal ion or a tetraalkylammonium ion (in which each alkyl group may be the same or different and each has from 1 to 20 carbon atoms), and n stands for an integer equal to the positive valency of M; to give a compound of formula (Ia):

in which R^(1a) and R^(2a) are as defined above; and, if necessary, removing protecting groups; and, if necessary, any of the following steps (i) to (v): (i) converting the group R^(1a) to any of the other groups represented by R¹; (ii) where R² represents an alkyl group, alkylating the product; (iii) where R³ represents an alkyl group, alkylating the product; (iv) where R³ represents an alkoxy group, alkoxylating the product; (v) salifying the product to give a pharmaceutically acceptable salt of the compound of formula (I). 